From the Avaya Support Site
To power down your Serenade, follow these steps:
Issue a "Shutdown" command at the @ prompt. This will take the system out of service.
Using the power switch on the front of the cabinet, turn the system off.
Disconnect the system from the power source.
To bring the system back up when it is safe to do so and power is stable:
Connect the system to the power source.
Using the power switch on the front of the cabinet, turn the system on.
When the system has completed initialization, issue a "Startup" command at the @ prompt.
This will put the system back in service.